That's the opposite of what I'm saying. Checking the night side of a planet for visible light isn't useful because a technological civilization won't necessaril

That's the opposite of what I'm saying. Checking the night side of a planet for visible light isn't useful because a technological civilization won't necessarily create large amounts of light pollution the way we do. If we happen to see nighttime light pollution that would be useful, but planning a mission around looking for it specifically would not make sense.